If you remove the bulb for the rear deck 3rd brake light you get an annoying warning light on the dash. Obviously you want to remove this bulb when installing a spoiler.



I couldn't find any info on this other then people recommending to replace the bulb with a resistor.
The FSM isn't clear since the car is prewired for both the rear deck 3rd brake light and spoiler light.

The fix is to replace the stop/tail lamp unit with one from a car with factory spoiler. You can leave the rear deck 3rd brake light bulb installed and it will not illuminate and no more warning light.

White label from car with spoiler.
Orange label from car with NO spoiler.

 

Does the spoiler do anything or just a for show?

 

Researching that sensor gets interesting. In the parts listing,

Part number 28425-5Y700 (white label in photo) is specified for a 2002 SES & SEL model with no reference to transmission. No other models are listed, either.

Part number 28425-5Y701 (not shown in photo) is specified for a 2003 SES & SEL model with no reference to transmission.

Part number 28425-5Y710 (orange label in photo) is specified for a 2003 GLE & GXEL model with no reference to transmission.

I can understand there being a difference between the SE and the other models as the spoiler adds more light bulbs and would have more current draw.